Shiro Yoshida was exposed to radiation while in utero, and learned of his mutant powers as an adolescent. His father traveled often and Shiro was fed anti-American sentiments by his nationalist uncle Tomo. He first joined the X-Men temporarily to rescue the original X-Men from the sentient island of Krakoa. Later he was a member of X-Corp, though he has resisted becoming a core member of the X-Men. His cousin is the Silver Samurai.